Armadillos are very useful as a food source for vultures.

And, as to the thread's original topic, there's no economic justification for the trade in large constrictors. If people want snakes as pets, there are numerous native snakes which make better, safer pets. If they'd cultivate the market for king snakes and rat snakes, breeders and pet stores could make just as much money as they do from pythons. And if the owner gets tired of a corn snake and turns it loose in the wild, it's certainly not going to harm the environment. It's probably still not good for the snake since a released captive animal won't be as adept at finding prey as its wild cousin and won't have a healthy fear of snake hating humans, but the worst possible result is a dead snake. More vulture food!